1. Field of the Invention
The present invention generally relates to a data recording apparatus and, more particularly, to a data recording apparatus for recording data on tracks of a recording medium, e.g., an optical card, an optical tape, or a magnetic card, with a predetermined data arrangement.
2. Description of the Related Art
Optical cards, optical tapes, magnetic cards, and the like are known as recording media for recording data. Of these media, optical cards and magnetic cards are widely used because they are convenient to carry. Especially, magnetic cards are widely used as credit cards and prepaid cards. With regard to optical cards, a variety of applications in the field of finance and medicine are considered because they have large recording capacities.
For example, a method of recording data on the optical cards is disclosed in Unexamined Japanese Patent Publication (KOHYO) No. 58-500462 (National Publication of Translation Version by PCT). According to this method, data is recorded on tracks by moving an optical card and a recording head relative to each other.
In general, when data is to be recorded on a recording medium, such as an optical card, which is constituted by a plurality of linear tracks, a recording time required to record data in two directions of the relative reciprocating motion of the optical card and the recording head is shorter than that required to record data in only one direction of movement.
More specifically, according to this recording technique, when, for example, an optical card 1 is to be reciprocated in relation to a recording head 2 to record data as shown in FIGS. 4A and 4B, the data is recorded on tracks 3 on the optical card 1 in two directions, i.e., in a forward motion (forward direction) shown in FIG. 4A and a backward motion (backward direction) shown in FIG. 4B, in accordance with the same modulation rule in the respective directions. In such a recording technique, however, since data is recorded in opposite recording directions, the recording direction of data on a given track cannot be identified. In a reproducing operation, therefore, a data read operation cannot be performed unless some specific means is provided.
For this reason, for example, flags 5 and 6 for discriminating recording directions are recorded on the start and end portions of a data block 4, as shown in FIG. 5, so that a data read operation can be performed upon discrimination of recording directions on the basis of these flags. In such a technique, however, since areas for recording the flags 5 and 6 are required, the recording capacity of each track 3 is reduced accordingly. In addition, since this technique requires a circuit for recording the flags 5 and 6 and a circuit for discriminating a flag in a read operation, the apparatus becomes complicated and expensive.
In order to solve this problem, Published Unexamined Japanese Patent Application No. 63-187463 discloses a technique of recording data by switching data arrangements and modulation rules in accordance with the direction of the relative movement of a cardlike recording medium and a recording head. This technique will be described below with reference to FIG. 6.
FIG. 6 shows a modulation circuit based on MFM (Modified Frequency Modulation). Referring to FIG. 6, reference numeral 7 denotes a buffer memory for storing data to be recorded; 8, a parallel/serial converter for converting parallel data output from the buffer memory 7 in a predetermined order into serial data; and 9, a modulator for modulating the serial data. In this modulation circuit, the order of reading out data from the buffer memory 7 is switched to another order in accordance with a direction indicating signal. Upon reception of the direction indicating signal, the parallel/serial converter 8 switches conversion directions, i.e., sequentially converts the parallel data from the most significant bit into a serial bit string (forward direction) or sequentially converts the parallel data from the least significant bit into a serial bit string (backward direction). The modulator 9 receives the direction indicating signal and switches conversion rules for the serial data output from the parallel/serial converter 8. The modulated data obtained by the modulator 9 is data modulated by normal MFM in forward recording. In backward recording, the modulated data is identical to the modulated data in forward recording when viewed from the direction opposite to the backward recording direction. According to this technique, therefore, data can be recorded on tracks with a predetermined data arrangement regardless of recording directions.
Although this technique can be applied to fixed word length codes in MFM, it cannot be applied, as it is, to variable word length codes in 2-7 modulation. This is because the bit length of original data to be modulated varies depending on the contents of original data.
In order to solve such a problem, data of one sector may be modulated as a whole, so that when modulated data is to be read out, orders of reading the data are switched in accordance with recording directions. In this technique, however, modulating and recording operations cannot be simultaneously performed, leading to an increase in recording time. In addition, according to this technique, since the storage capacity of a storage means, e.g., a random-access memory (RAM), for temporarily storing modulated data is increased, the cost of the apparatus is increased.